The present invention relates to a method of positioning a plurality of workpieces in a predetermined alignment and will be disclosed in connection with a mechanism for treating and aligning flattened square pieces of thermoplastic resin for placement upon a conveyor.
In the processing of thermoplastic resin, an especially quick method of forming thermoplastic containers or other articles has developed which utilizes extruded or coextruded square chips or blanks. These chips are heated to a temperature above their softening point but below the melting point to facilitate subsequent biaxial orientation of the chip material in a forging and forming process. The chips are forged into a preform from which the final product, such as a container, is thermoformed. This process has been termed "scrapless thermoforming" and is more fully described in U.S. Pat. Nos. 3,739,052 and 3,947,204.
Transfer of the workpiece or chips from the thermal conditioning process must occur in such a way that the chip retains uniformity of temperature, is not unduly or unevenly chilled, and suffers no appreciable temperature drop nor any physical distortion from its flattened state. The ultimate product, which may take the form of a deep dish or tub of the type used for butter, cottage cheese and margarine, may be substantially distorted or defective if the chip is subjected to thermal nonuniformity. Hence, the transfer mechanism used to transport the chip throughout this process should work fast enough to minimize temperature changes and heat losses while at the same time avoiding physical distortion of the workpiece.
In order to realize these multiple objectives, the present invention provides a mechanism for precision placement and alignment of the workpieces upon a transport member immediately prior to the thermal conditioning. Such an alignment permits a second transfer mechanism to rapidly translocate the chips from the transport member following the heating process, to a forge with minimal physical distortion and heat loss.